Sheds don't contain any living tissue, though. This is not trivial, but part of my personal research.
Epithelial cells, while easy to collect, would only provide results relating to compounds that could be injested(getting into the snake's mouth). Blood cells are last on the list since they do not come into contact w/anything but what could make it into the bloodstream(from laceration). I am more interested in epidermal tissue.
I would never subject any living creature to needless trauma. I suppose this is not an appropriate forum to post my query and will continue along veterinary venues.